Extreme pressure lubricant



Patented 1941 :Netherlands. assignorsto Shell Development Company, Sancorporation of Delaware No. Drawing orlgincl applieation August .2,

1937, Serial N0; 158,958.: .Dlvlded'and this-applloation January In theNethcrlandslAugust g9, v

. "loamy crass-w ll t bnir'elates to lubricants suitable'Iherelative-pos'ition bi its for lubrication under-very high prwsuresand at elevated temperatures; and-is .a division ofpour copendingapplication, No. 156,958; Kflled August "2, 1937;" Patent No. 2,194,418;issued- March 26. 1940.

It has already v catingoils and greasessubstances known as exe tremepressuresubstances, which prevent seizure and scoring of metals whichare in motion we; tive to each other under very high pressures. Most ofthe substances heretofore suggested contain halogen, sulfur orphosphorus in a'form conducive to corrosion. The thought generallyprevailed that these elements give rise to a. chemical reaction to formproducts which keep the metals separated when the ofl film gives wayunder excessive pressures; It was reasoned that since a chemicalreaction essential to the working of an extreme pressure lubricant, acertain amount of corrosionfisQ-indispensable for. the activity ofextreme pressure substances.

been proposedf to add to lubri molecule to have little-1f. any.influence,-

corrosive properties, particularlyso if they possess two or morecarboxyl radicals; It, furthermore, the i compounds are structurallycompact. they are also highly resistant tqjthermal decomposition at theelevated temperatures normally encountered in the'lubrication ofinternal com- It has further been proposed "to use oxyhydrocarbons suchas fatty acids, cresols, phthalic acid,

etc., for the purpose ofenhancing the power of exteme pressuresubstances. However, these oxyhydrocarbons, when used by themselves,have little, if any, effect in the matter of inducing extreme pressureproperties in mineral oils.

It is the p se ofthis invention to provide. extreme pressure lubricantswhich are free from corrosiveness andwhich for their effectiveness}apparently do not rely, orrely only partialimon and the a chemicalreaction between the metals extreme pressure substances.

We have discovered that aromatic compounds built up of at leasttwo6,-carbon rings and said' compound containing at least'two hydroxyl-containing radicals havingjnot' more thanone carbon atom between thehydroxyl groups and the rin substituted in the same or different ary'lrings, 1. e. the hydroxy'groups may be attached directly tothe ring asin phenols or may be part.

bustion' engines and are therefore especially valprovided they a epresentin'theirf form and not bound as esters,-salts,,etc. lThecompounds'of our invention -areinon-feorw; rosivetowardssteel,bronze-and va'r1ous bearing nrieta'ls and in manyinstances'havfe-positive anti;-

uable for use in" crankcase lubricants for internal:

combustion engines.

Due to the fact that our compounds possess two or more hydroxyl orcarboxyl radicals they havehigh. boilingjtemperatures, and most of themare substantially non-volatile. This is of obvious advantage inlubricating oils to be'used in internal combustion engines.

The solubility of our compounds in hydrocarbon oils is quite low andtherefore they are usually used in the form for suspensions rather thansolutions. Suspensionsmay be prepared'in any suitable manner, asby'dispersing the coincolloid mill, or by dissolving them, inaiiuitualsolvent, etc. Substances having a stabilizing feet onthesuspension so produced, such as "-quantities. ofv fattyacids of the-typeof stearic acid,':may'be-added toadvantage. Owing-to their powerto"preserve the suspension, such subs i stances have frequentlytheadditional eflect of, enhancing the extreme pressure properties ofourcompounds, particularly atelevated temperatures, when the suspensionstend to become unof a carbo-hydroxyl' group as in benzoic acid or benzylalcohol show good extreme pressure qualities when added to lubricatingoils in quantities 1 substantially above 1%. While the presence of twoof the hydroxyl radicals is suflicient 'toimpart iothe polycyclic.-compounds extreme pressure properties, additional hydroxylradicals'improve this property.

Thus between two substances of equal molecular structure but differingin the number of attached hydroxyl radicals, those containing the largernumber of hydroxyls are in general more active.

stable. I a t It has been stated hereinbefore that-the two or morefi-carbon rings ofour eompoundswshould stand in' close proximity of eachother. By this a we mean that the earbocyclic rings should preferably beseparated from each other by a chain or chains of notmorethan two atomsoian element normally capable of firmly linking 6-carbon rings toproduce stable compounds, said element having an atomic number below 17.Thus compounds containing two or more G-carbon rings which are separatedby'two or less carbon or nitrogen atoms, or by}; single atom of thegroup consisting of oxygen, sulfur and phosphorus, not forming part ofthe ring, or which are advantageously linked directly without anintermedipounds in the lubricating oil witlrthe aid-feta ate atom as indiphenyl, vor by common carbon.

atoms as in naphthalene. are known to be very stable in the absence orother unstable linkages or radicals. While many. compounds are known inwhich the rings are separated by other elements, having atomic numbersabove 16 capable oi linking 6-carbon rings, such as As, Sb. Hg. Pb,etc., we have found that such compounds, although sumciently stable formany purposes are not suflicientiy stable to be of practical use inlubrication, particularly at high temperatures or in the presence oimoisture, notwithstanding that all of them exhibit extreme pressureproperties,

provided they have the necessary hydroxyl radicals; and still othercompounds in which the link is formed by elements having atomic numbersbelow 17, other than those enumerated above, such as Mg, Al, Si, areknown to be extremely unstable, some of them igniting in contact withair, and others rapidly hydrolyzing in contact with water.

Derivatives containing the necessary hydroxyl radicals ofdiphenylethane, diphenylmethane, triphenylmethane, diphenyl,naphthalene, tetraline, anthracene, phenanthrene, picene, chrysene,acridine, phenacine, diphenyloxide, dinaphthyloxide, diphenylsuliide,dinaphthylsulflde, carba-.

zol, azobenzol, triphenylphosphine. or homologues of these compounds areexamples of suitable compounds.

In addition. the rings may contain short aliphatic side chains.relatively long side chains of more than 2 carbon atoms being veryundesirable as they greatly lower the thermal stability of ourcompounds.

The presence of polar radicals other than hydroxyl of the type describedin our compounds may be permissible but is usually of little advantageand in many instances of decided disadvantage. For instance, aminoradicals frequently reduce the resistance our compounds towardoxidation, halogens tend to make them corrosive, nitro radicals lowerthe thermal stability, etc.

The quantity of our compounds required to impart to minerallubricatingoils high pressure resisting properties normally variesbetween about 1 to 10%. r

In the following examples, which illustrate our invention. results areshown of tests, made in the Boerlage four-ball apparatus described inEngineering. July 14, 1933, with a straight mineral lubricating oil andblends thereof with various compounds of the group herein described.

Example I A 4% suspension of a methylene dibetanaphthol in a Venezuelanbright-stock gave a welding pressure of 300 kg., whereas the unblendedoil permitted welding at 150 kg.

Example II The family of diphenyl methane derivatives provides a largenumber of suitable compounds which may be obtained by condensingpolyphenols, as hydroquinone, resorcine, pyrocatechin, phloroglucine,pyrogallol; or carboxyl phenols as salicylic acid, cresotic acid, gallicacid,

or naphthols, naphthoic acids, hydroxy anthracene, alizarine, etc.; witha lower aldehyde such as formaldehyde or acetaldehyde. Also mixtures ofvarious phenols may be condensed.

For instance, a mixture of 3 parts of resorcine, 1 part of a 40% aqueoussolution of formaldehyde and 20 parts of an 8% aqueous hydrochloric acidis allowed to stand for several hours, during which time a precipitateof methylene diresorcine is formed, which is filtered of! andrecrystallized from ethyl alcohol. The product obtained consists ofmicroscopic crystals. A 4% suspension thereof in the brightstock ofExample I raised the welding pressure to 500 kg. All parts are byweight.

Example 111 180 grams of salicylic acid are heated on a steam bath for.40 hours with grams of a 30% aqueous formaldehyde solution and 640milliliters concentrated hydrochloric acid. The crystalline salicylicacid is slowly converted to a sandy powder containing methylenedisalicylic acid, which is washed with water to remove the freehydrochloric acid, dissolved in dilute ammonia, filtered andreprecipitated with dilute sulfuric acid. A 4% suspension of the productin the lubricating oil oi Example I gave a welding pressure of 600 kg.

Example 1v Methylene digallic acid, obtained in a manner similar to theprocedure described in Example IV, in a 4% suspension in the lubricatingoil of Example I gave a welding pressure of 500 kg.

Example V Another large class of suitable compounds known as the rosolicacids or aurines, which are derivatives of triphenyl methane, may beobtained by condensing phenols or carboxyl phenols with oxalic acid inthe presence of a condensing agent such as sulfuric acid, zinc chloride,etc. A 4% suspension of aurine or pararosolic acid raised the weldingpressure in the lubricating oil of Example I to 400 kg.

Example VI

